It sounds like the implication is that the son of a bitch is a worm — as in an invertebrate which lives under rocks in damp soil because sunlight and dry air are too hot and dry for it.
The metaphor is that the SOB inherited a lot of money when his father died, and he's using it to protect himself from the consequences of his actions. The narrator is likening this money to a rock protecting a worm from the sun. If the narrator pulls off the rock (exposes the SOB somehow, by taking away his money, maybe?), then the "light of day" (public exposure) will hit the worm (the SOB) and make things hot and uncomfortable (expose him for being a fraud, disrupt his posh lifestyle).